From mboxrd@z Thu Jan 1 00:00:00 1970 From: Anthony Liguori Subject: Re: Diff between std, xen0 and xenU kernel Date: Tue, 08 Feb 2005 14:46:13 -0600 Message-ID: <42092515.9070108@us.ibm.com> References: <42091058.2020503@rptec.ch> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit In-Reply-To: <42091058.2020503@rptec.ch> Sender: xen-devel-admin@lists.sourceforge.net Errors-To: xen-devel-admin@lists.sourceforge.net List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , List-Archive: To: Jean-Eric Cc: xen-devel@lists.sourceforge.net List-Id: xen-devel@lists.xenproject.org Jean-Eric wrote: > I have a question: > What is the difference between a std Linux kernel and an xen0 one? > Except that we can run xenU instances in the xen0 one... A standard Linux kernel expects to manage it's own memory, hardware, etc. A xen kernel knows that it's in a hypervisor so it makes hypercalls when it needs to deal with those sorts of things. That's a pretty gross simplification but you can check out any number of the papers referenced on the Xen homepage for whatever level of detail you want. > And is the xen0 instance different from the xenU instances? Or is it > just another xenU instance in fact? A little bit. It mostly has to do with the initrd setup code. However, I think there was a thread on a list where someone said you could in fact use a xen0 kernel within xenU if you had the right drivers enabled. Really, the biggest difference is that xen0 domain has backend device drivers and the xenU kernel has the front-end version of those drivers. > And if I run programs in the xen0 instance, will it degrade perf of > xenU instances? Or render them less secure (in term of isolation)? It shouldn't decrease performance. Currently, xen0 is pretty much a single point of failure though. If you had a remote comprimise in xen0 then an attack could bring down every other domain. Regards, Anthony Liguori ------------------------------------------------------- SF email is sponsored by - The IT Product Guide Read honest & candid reviews on hundreds of IT Products from real users. Discover which products truly live up to the hype. Start reading now. http://ads.osdn.com/?ad_id=6595&alloc_id=14396&op=click